Charged particle blocking element, exposure apparatus comprising such an element, and method for using such an exposure apparatus

ABSTRACT

The invention relates to an exposure apparatus and a method for projecting a charged particle beam onto a target. The exposure apparatus comprises a charged particle optical arrangement comprising a charged particle source for generating a charged particle beam and a charged particle blocking element and/or a current limiting element for blocking at least a part of a charged particle beam from a charged particle source. The charged particle blocking element and the current limiting element comprise a substantially flat substrate provided with an absorbing layer comprising Boron, Carbon or Beryllium. The substrate further preferably comprises one or more apertures for transmitting charged particles. The absorbing layer is arranged spaced apart from the at least one aperture.

CLAIM FOR PRIORITY

This application is a continuation of application Ser. No. 16/638,124,filed Feb. 10, 2020, which is a national stage filing under 35 U.S.C. §371 of International Application No. PCT/JP2018/024475, filed on Jun.21, 2018, and published as WO 2019/031093 A1, which claims priority ofU.S. Provisional Application No. 62/542,310, which was filed on Aug. 8,2017, which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The invention relates to a charged particle blocking element for use ina charged particle optical arrangement for projecting a charged particlebeam onto a target. The invention further relates to an exposureapparatus for projecting a charged particle beam onto a target, whichexposure apparatus comprises a charged particle blocking element, andrelates to a method for projecting a charged particle beam onto a targetusing such an exposure apparatus. In addition, the invention relates toa method of manufacturing a semiconductor device and/or a method forinspecting a target by means of such an exposure apparatus.

BACKGROUND

In the semiconductor industry, an ever increasing desire exists tomanufacture smaller structures with high accuracy and reliability. In acharged particle beam exposure apparatus, a target surface can beexposed to one or more charged particle beams directed to and focused onthe target surface with high accuracy. In addition, the use of chargedparticles allows to obtain a much higher resolution and precision fortransferring or analyzing a pattern on the target surface, when comparedwith an exposure apparatus which uses light for exposing the targetsurface.

However, to be commercially viable, the charged particle exposureapparatuses need to be able to meet challenging demands for substantialwafer throughput and stringent error margins, both for lithographysystems and for inspection systems. A higher throughput may be obtainedby using more charged particle beams in the exposure apparatus, andhence by using more current.

However, an increase in the current results in more charged particlesthat interact with components in the exposure apparatus. Collisionsbetween charged particles and system components inside the exposureapparatus may cause significant heating of respective components.

Problems related to heating of components within charged particle beamsystems are generally addressed by actively cooling such components, asdescribed in for example the granted U.S. Pat. Nos. 8,558,196 and9,165,693 as well as in the International Patent Application publishedas WO2013/171216.

In an article by M. van Zaalen in “VAN TEKENTAFEL NAAR OVEN”, LinkMagazine, XVIII:1 (February 2016), page 28 and 29, the problem ofheating of the collimator lens in a maskless multi-electron-beamlithography system is identified, caused by the high electric fieldwithin the collimator and the high current of the electron beam beingfocused by the collimator. As also indicated in the article of M. vanZaalen, not all the electrons of said charged particle beam(s) passthrough the collimator, but some are reflected within the collimator.This phenomenon also contributes to the heating of the collimator. Theheating of beam manipulation components may lead to thermal deformationsthat reduce the accuracy of the exposure process. As described in thearticle of M. van Zaalen, this was solved by a re-design of thesuspension of the collimator within the lithography apparatus. Thecooling of the collimator was therein improved by enabling heat to beremoved from the collimator by thermal conduction via the modifiedsuspension.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a charged particleexposure apparatus, as well as a component therefor, which at leastpartially reduces heating of the components within the exposureapparatus. Charged particles should be understood as encompassing bothelectrons and ions. When reference is made to a charged particle beam,this could be made up of either electrons or ions. The present inventionis in particular related to electron beam exposure apparatuses,including electron (multi-)beam lithography systems, various types ofelectron microscope, and inspection systems. The invention can howeveralso be applied in systems using other types of charged particles,including positively or negatively charged ions, for example Heliumions.

According to a first aspect, the invention provides a charged particleblocking element for blocking charged particles, wherein the chargedparticle blocking element comprises a substrate, wherein the substratecomprising at least one aperture allowing passage of charged particles,wherein at least a portion of a surface of the substrate is providedwith an absorbing layer of a material comprising Boron, Carbon orBeryllium, wherein the absorbing layer is arranged spaced apart from theat least one aperture, and wherein at least part of the surface of thesubstrate which is provided with the absorbing layer comprises anelectrically conductive material.

The absorbing layer at least partially absorbs the charged particlesimpinging thereon. That is, the layer is functional for receiving thecharged particles impinging thereon, the charge of which is passed on tothe conductive material in order to be transported away from the chargedparticle blocking element. The conductive material may be realized byproviding the substrate located underneath the absorbing layer with anelectrically conductive layer, or by providing the substrate as at leastpartially electrically conductive, e.g. wherein at least part of thesurface provided with the absorbing layer is electrically conductive.

The charged particle blocking element is suitable for blocking chargedparticles in a variety of applications. It can be used for at leastpartially blocking a beam of charged particles along its trajectorywithin a charged particle exposure apparatus and/or inspectionapparatus. This may be for shaping a beam or a plurality thereof such asin a current limiting aperture array element. For example it can be usedin one or more of the aperture arrays in a system as described in U.S.Pat. No. 8,653,485 B2, in particular in an aperture array 4A of a systemas illustrated in FIG. 12 of U.S. Pat. No. 8,653,485 B2. It can also beused as a shutter element for temporarily switching off a beam or a beamsource by entirely blocking the same without a need of switching off thesource itself. This may especially be advantageous where switching onthe source normally comes with noticeable settling time. In a system asillustrated in FIG. 12 of U.S. Pat. No. 8,653,485 B2, it could bearranged at a location between the source 1 and the collimator 3.

In particular in case the charged particle blocking element is used as acurrent limiting aperture, it is advantageous to arrange the absorbinglayer spaced apart from the at least one aperture in the substrate.Accordingly, it can be at least substantially prevented that material ofthe absorbing layer is arranged at the edge or overhanging the edge ofthe at least one aperture, or is arranged inside the at least oneaperture, where said material may distort and/or disrupt a chargedparticle beam which traverses said at least one aperture.

In particular, the absorbing layer is arranged at a surface of thesubstrate which, in use, will be arranged facing the charged particlesource. Accordingly, when the charged particle blocking element is usedfor blocking at least a part of a charged particle beam from a chargedparticle source, it can be arranged such that at least a large part ofthe blocked part of the charged particle beam impinges onto theabsorbing layer. Accordingly, it is preferred that the absorbing layeris arranged in a near vicinity of the at least one aperture.

Surprisingly, the inventors have found that, when using an absorbinglayer of a material comprising Boron, Carbon or Beryllium to block atleast part of the charged particle beam, the heat load on chargedparticle optical components arranged between the charged particleblocking element and the charged particle source, is strongly reduced,as compared to a charged particle blocking element without such anabsorbing layer. This holds true in particular to charged particleoptical components directly adjacent the charged particle blockingelement and/or having an unobstructed line of sight to the chargedparticle blocking element. By reducing the heat load on these chargedparticle optical components, the exposure apparatus can be operatedduring a longer period of time without the charged particle opticalcomponent becoming excessively heated and/or cooling of the chargedparticle optical component is less critical.

As discussed above, the primary object leading to the present inventionwas to reduce the heat load on components within a charged particleexposure system, for example an exposure system as described in U.S.Pat. No. 8,653,485 B2, U.S. Pat. No. 8,558,196 B2, U.S. Pat. No.9,165,693 B2 and WO2013/171216. This was achieved by a charged particleblocking element as described herein, in particular when used in acurrent limiting aperture array. In addition, the inventors have found asubstantial reduction of aberrations of the charged particle beams onthe surface of the target when using the absorbing layer of a materialcomprising Boron, Carbon or Beryllium to block at least part of thecharged particle beam. Hence, further to the primary effect of reducingheat load, a secondary effect of reducing aberrations of chargedparticle beams within the exposure system was observed. Further, bothheat load as well as aberrations has been observed to be reduced even ifthe surface receiving the charged particle beam is only partially coatedwith the absorbing layer. It is however preferred that the majority ofthe blocked charged particle beam impinges on the absorbing layer.

The findings of the inventors seem to suggest that the heating of thecomponents upstream of the charged particle blocking element withrespect to the beam of charged particles, and a forming of space chargewhich may disturb charged particle trajectories, may be caused bybackscattered charged particles and/or secondary electrons generated bythe part of the charged particle beam which is blocked by the chargedparticles impinging on the charged particle blocking element. Secondaryelectrons may result from backscattered charged particles impinging on asurface of another element within the system. By providing an absorbinglayer according to the invention on the side of the charged particleblocking element which in use receives the charged particles to beblocked, at least the amount of backscattering may be reduced.

It is noted that an absorbing layer of a material comprising Boron,Carbon or Beryllium within the context of this application alsoencompasses an absorbing layer of a material comprising a combination ofBoron, Carbon or Beryllium with one or more other elements, such asBoron Nitride or Silicon Carbide.

Preferably, the absorbing layer comprising Boron. In particular, theabsorbing layer is a Boron layer or a Boron Nitride layer. Preferablythe absorbing layer is a Boron coating or a Boron Nitride coating. Acoating is a thin layer, or covering, typically having a thickness ofsome tens or hundreds of nm, applied to the surface of an object. TheBoron layer or Boron coating is preferably a substantially pure Boronlayer. Boron is advantageous because it is non-toxic, is stable at roomtemperature, does not oxidize in air, and can be applied using knowntechniques such as sputtering or vapor deposition.

A disadvantage of using a Boron or Boron Nitride layer for blockingcharged particles is the relatively high electrical resistivity of thesematerials, which makes these materials not an obvious choice when one issearching for a material for blocking a charged particles. In use, theabsorbing layer will become electrically charged by the chargedparticles which impinge on said layer, and when using an absorbing layerof a material with a high electrical resistivity, this electrical chargeis difficult to remove via electrical conduction through said absorbinglayer.

A further insight underlying the present invention, apart from a measureto combine such layer with an electrically conductive layer orsubstrate, therefore holds that the thickness of the absorbing layershould be selected with care.

Advantageously, the absorbing layer has a thickness sufficient toprevent backscattering of said charged particles from a portion of saidsubstrate located below said absorbing layer and thin enough forelectrical charge of said charged particles to be received by saidelectrically conductive surface. This allows efficient absorption ofcharged particles, that is, a very low amount of backscattering ofcharged particles, while at the same time avoiding charge accumulationin the absorbing layer by removal of the absorbed electrical charge viasaid electrically conductive surface. Although the probability ofbackscattering is reduced with increasing thickness of the layer, atleast up to a stabilizing threshold, increasing the thickness of thelayer reduces the electrical conductivity through the thickness of thelayer. If the absorbing layer becomes too thick, it will substantiallyact as an electrical insulator.

In an embodiment, the absorbing layer has a thickness between 100 nm to500 nm. In a more preferred embodiment, the absorbing layer has athickness between 150 and 250 nm. It has been observed that an absorbinglayer thickness in this range provides a reduced heating of chargedparticle optical elements arranged between the charged particle blockingelement and a charged particle source, while avoiding charge build-up inthe charged particle blocking element.

In an embodiment, at least a part of the substrate is electricallyconductive. This ca be realized by providing the substrate by aconductive, e.g. metallic, material, by the substrate comprising anelectrically conductive material, or by a highly doped semiconductorsubstrate, which is highly doped at least in the area on which theabsorbing layer is provided. For example, highly doped Silicon may beused. Accordingly, the substrate can assist in removing electricalcharge from the absorbing layer. Preferably, the substrate comprises aconnecting part for connecting the substrate to a voltage supply or toground potential. In an embodiment, the connecting part comprises aconnecting area, also referred to as contact area preferably formingpart of or being arranged on a surface of said substrate, whichconnecting area is configured for connecting the substrate to a voltagesupply or to ground potential. In particular connecting the electricallyconductive substrate to ground potential enables the removal ofelectrical charge from the absorbing layer via electrical conductionthrough said substrate.

In an embodiment, the substrate is provided with an electricallyconductive layer, wherein the electrically conductive layer is at leastpartially arranged in between the substrate and the absorbing layer.Accordingly, the electrically conductive layer can assist in removingelectrical charge from the absorbing layer. Preferably, the electricallyconductive layer comprises a material comprises Molybdenum (Mo) orChromium (Cr). It may be formed by substantially pure Molybdenum orChromium, or it may be formed of a material comprising at least one ofthese elements. In particular Molybdenum is preferred because Molybdenumoxide is also electrically conductive which ensures that the layer ofMolybdenum is electrically conductive even when the molybdenum is atleast partially oxidized. In this embodiment the substrate propertiesrelating to electrical conductivity are of less importance. In thisembodiment the substrate may be for example a semiconductor substratehaving a relatively low or substantially no doping.

Since the electrically conductive layer is at least partially arrangedin between the substrate and the absorbing layer, the absorbing layercan act as a protective coating for the electrically conductive layer.Accordingly, the absorbing layer can provide a protection for theelectrically conductive layer against oxidation, at least for the partwhich is covered by the absorbing layer, which allows to also use otherconductive materials for the electrically conductive layer, such asCopper (Cu) or Aluminum (Al).

Preferably, the charged particle blocking element comprises a connectingpart or area which is electrically conductive and connected to theelectrically conductive layer, which connecting part or area isconfigured for connecting the electrically conductive layer to groundpotential or to a controlled voltage, to assist in the removal ofelectrical charge in the absorbing layer via electrical conductionthrough said electrically conductive layer. In an embodiment, theconnecting part comprises a connecting area, also referred to as contactarea, preferably forming part of or being arranged on the substrate,which connecting area is configured for connecting the electricallyconductive layer to a voltage supply or to ground potential.

In an embodiment, the substrate comprises a Silicon (Si) wafer. A Siwafer provides a flat and mechanically stable substrate, which canreadily be provided with apertures using etching techniques known in theart. This is in particular advantageous in applications where thecharged particle blocking element is provided with a plurality ofapertures. Such a charged particle blocking element can be used as acurrent limiting element, as will be discussed below. Since Si usually ahigh electrical resistance, at least when the Si is not doped, the Siwafer substrate is preferably provided with the electrically conductivelayer, the absorbing layer being arranged on the electrically conductivelayer, as described above.

In an embodiment, the substrate is provided with at least one apertureallowing passage of charged particles. The charged particle blockingelement may be arranged within a charged particle beam path such as toallow passage of at least a portion of the charged particle beam throughthe at least one aperture, while enabling at least partial and/ortemporary blocking of the charged particle beam by non-aperture areas onthe substrate. When the aperture allows passage of only a portion,generally the central portion, of the charged particle beam whileblocking the other portions of the beam, it is often referred to ad acurrent limiting aperture.

In an embodiment, the substrate is provided with a plurality of saidapertures arranged to form one or more aperture arrays, each of said oneor more aperture arrays arranged in a corresponding array area, oraperture array area, of said substrate. Such element may be used as acurrent limiting aperture array within a charged particle beam system.For example, it may be used for splitting a charged particle beam into aplurality of charged particle beams.

The absorbing layer preferably at least partly encloses said arrayareas. In some applications the charged particle beam is larger than thearea encompassing the one or more aperture arrays, such that a largepart of the charged particle beam blocked by the blocking element fallsonto the absorbing layer even if this would not extend onto surfaceareas located between individual apertures or array areas. Suchembodiment may be easier to manufacture, avoiding parts of the absorbinglayer extending into the apertures. As mentioned above, such partialcoverage of the charged particle receiving surface by the absorbinglayer has been observed to provide a substantial reduction in heating ofcomponents and/or aberrations of charged particle beams.

In further embodiments, each array area is at least partly enclosed bysaid absorbing layer. In still further embodiments, the absorbing layeris further arranged at least partly within each aperture array area.This may increase the portion of the charged particle beam beingabsorbed by the charged particle blocking element.

In an embodiment, the charged particle blocking element comprisescooling conduits for cooling at least the substrate. Preferably, thecooling conduits are arranged in thermal contact with the absorbinglayer and/or the substrate. Accordingly, the charged particle blockingelement can be provided with cooling conduits for guiding a coolingfluid (such as water) through said cooling conduits for removing heatfrom the charged particle blocking element. In an embodiment, thecooling conduits are arranged at a surface of the substrate facing awayfrom the absorbing layer. In an embodiment of use in a charged particlebeam system, the cooling conduits are arranged at a surface of thesubstrate facing away from the charged particle source.

In an embodiment, the substrate is provided with a further electricallyand/or heat conductive layer, wherein the further electrically and/orheat conductive layer is arranged in contact with the absorbing layerand with the cooling conduits. A heat conductive layer provides a heatconducting path from the absorbing layer to the cooling conduits. Thisembodiment allows using a substrate of a material having poor heatconducting properties. A further electrically conductive layer providesan electrically conducting path from the absorbing layer to the coolingconduits. Accordingly, the further electrically conductive layer canassist in removing electrical charge from the absorbing layer via thecooling conduits, which are usually connected to ground potential whenin use in an exposure apparatus. In addition, by electrically connectingthe absorbing layer to the cooling conduits no dedicated contact area orcontact arrangement is necessary at the side of the charged particleblocking element facing away from the side comprising the coolingconduits. Accordingly, the side of the charged particle blocking elementfacing away from the side comprising the cooling conduits can bearranged very close to an adjacent element or component of a chargedparticle optical arrangement.

According to a second aspect, the present invention provides a currentlimiting element for use in a charged particle exposure apparatus, saidcurrent limiting element comprising a substrate not allowingtransmission of charged particles, said substrate provided with one ormore apertures extending through said substrate from a first surface toa second surface of said substrate, said one or more apertures allowingpassage of charged particles, wherein at least a portion of said firstsurface is provided with an absorbing layer comprising Boron (B), Carbon(C) or Beryllium (Be), wherein the absorbing layer is arranged spacedapart from the one or more apertures, and wherein said absorbing layeris provided on an electrically conductive material or electricallyconductive surface.

It is noted that a current limiting element is usually used for limitingthe current in a charged particle beam. Accordingly the diameter of theone or more apertures is smaller than the diameter of the chargedparticle beam. Since the current limiting element at least partiallydefines the cross section of the charged particle beam that hastraversed said current limiting element, the apertures are usuallyprecisely manufactured. By arranging the absorbing layer spaced apartfrom the one or more apertures, any disturbances at least at the edge ofthe one or more apertures at least by the absorbing layer can beavoided.

The current limiting element according to the second aspect provides thesame or corresponding technical effects and advantages as the chargedparticle blocking element according to the first aspect described hereinabove. The charged particle blocking element of the first aspect,according to embodiments where the substrate is provided with one ormore apertures, may be used as the current limiting element according tothe second aspect.

The current limiting element according to the second aspect may becombined with one or more of the embodiments and/or alternatives of thecharged particle blocking element according to the first aspect.

According to a third aspect, the present invention provides a shutterelement for at least temporarily blocking a charged particle beam, theshutter element comprising a substrate, at least a portion of which isprovided with an absorbing layer comprising Boron (B), Carbon (C) orBeryllium (Be), wherein said absorbing layer is provided on anelectrically conductive surface on said substrate.

It noted that a shutter element in use is arranged for temporarilyallowing a charged particle beam to pass the shutter element and fortemporarily blocking the charged particle beam.

In the situation where the charged particle beam is allowed to pass theshutter element, the charged particle beam passes at least along an edgeor through an aperture of said shutter element. When the shutter elementis this situation is configured to act also as a current limitingelement, the absorption layer is preferably arranged spaced apart fromthe edge or the aperture. However, when the shutter element in thissituation is configured not to act as a current limiting element, inparticular when the charged particle beam is spaced apart from the edgeor the circumference of the aperture, the absorption layer may bearranged up to the edge or up to the circumference of the aperture.

The shutter element may be realized by the charged particle blockingelement of the first aspect.

The shutter element of the third aspect may be combined with one or moreof the embodiments and/or alternatives of the charged particle blockingelement according to the first aspect.

According to a fourth aspect, the present invention provides an exposureapparatus for projecting a charged particle beam onto a target, saidexposure apparatus comprising a charged particle optical arrangement forforming a charged particle beam and for projecting the charged particlebeam onto the target, wherein the charged particle optical arrangementcomprises a charged particle source for generating the charged particlebeam and a charged particle blocking element according to the firstaspect, which charged particle blocking element enables blocking atleast a part of the charged particle beam from the charged particlesource, a current limiting element according to the second aspectarranged to limit a charged particle current of said charged particlebeam, and/or a shutter element according to the third aspect.

In an embodiment, the absorbing layer of the charged particle blockingelement, the current limiting element, and/or the shutter element isarranged at a surface of the substrate facing towards the chargedparticle source and/or a source of backscattered and/or secondaryelectrons within the apparatus.

In an embodiment, the charged particle blocking element comprises one ormore apertures arranged as a current limiting aperture or currentlimiting aperture array of the exposure apparatus.

In an embodiment, the charged particle blocking element and/or thecurrent limiting element comprises an array of apertures for splittingthe charged particle beam into multiple charged particle beams.Accordingly, the charged particle blocking element and/or the currentlimiting element can be used for generating multiple charged particlebeams from a single large diameter beam. Typical applications arecharged particle multi-beam lithography systems, charged particlemulti-beam inspection systems, and charged particle multi-beammicroscopes.

In an embodiment, the charged particle optical arrangement comprises amodulation deflector for deflecting the charged particle beam onto thecharged particle blocking element, wherein the modulation deflector andthe charged particle blocking element are arranged to allow the chargedparticle beam to pass the aperture of the charged particle blockingelement when the charged particle beam is not deflected by thedeflector, and to at least partially block the charged particle beam bythe charged particle blocking element when the charged particle beam isdeflected by the deflector, or vice versa. Accordingly, the chargedparticle blocking element of this embodiment is used for modulating acharged particle beam, in particular for an on or off switching of acharged particle beam. Typical applications are charged particle(multi-) beam lithography systems.

According to a fifth aspect, the present invention provides a chargedparticle lithography system comprising an exposure apparatus or anembodiment thereof as described above.

According to a sixth aspect, the present invention provides a chargedparticle inspection system or charged particle microscope comprising anexposure apparatus or an embodiment thereof as described above.

According to a seventh aspect, the present invention provides a methodof projecting a charged particle beam onto a target using an exposureapparatus as described above, wherein the method comprises the step ofblocking at least a part of the charged particle beam from the chargedparticle source, wherein at least a part of the charged particle beamthat is blocked falls onto the absorbing layer of the charged particleblocking element or the current limiting element.

According to a eighth aspect, the present invention provides a method ofmanufacturing a semiconductor device by means of an exposure apparatusas described hereinbefore, the method comprising the steps of:

-   -   placing a wafer downstream of said charged particle optical        arrangement;    -   processing said wafer including projecting an image or a pattern        on said wafer by means of a charged particle beam generated,        shaped and/or modulated by said charged particle optical        arrangement; and    -   performing subsequent steps in order to generate a semiconductor        device by means of said processed wafer.

The subsequent steps of manufacturing a semiconductor device from saidprocessed wafer are known in the technical field of manufacturingsemiconductor devices. A number of said subsequent steps are for exampledescribed in the United States patent application No. US 2014/0176920 A1of the Applicant.

According to a ninth aspect, the present invention provides a method forinspecting a target by means of an exposure apparatus a describedhereinbefore, the method comprising the steps of:

-   -   positioning said target downstream of said charged particle        optical arrangement;    -   directing a charged particle beam generated and shaped by said        charged particle optical arrangement towards said target;    -   detecting charged particles transmitted, emitted and/or        reflected by said target upon incidence of the charged particle        beam on the target; and    -   performing subsequent steps in order to inspect said target by        means of data from the step of detecting charged particles.

The different embodiments described above can be combined. The variousaspects and features described and shown in the specification can beapplied individually, wherever possible. These individual aspects, inparticular the aspects and features described in the attached dependentclaims, can be made subject of divisional patent applications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of exemplary embodimentsshown in the attached drawings, in which:

FIG. 1 shows a schematic overview of an exposure apparatus according toan embodiment of the invention,

FIG. 2 shows a schematic overview of a microscope or inspectionapparatus according to an embodiment of the invention,

FIG. 3 shows a schematic cross section of an embodiment of a chargedparticle blocking element according to the invention,

FIG. 4 schematically illustrates blocking of a charged particle by acharged particle blocking element,

FIG. 5 shows a schematic cross-section of an embodiment of a part of acharged particle blocking element according to the invention,

FIG. 6 shows a schematic cross-section of a further embodiment of a partof a charged particle blocking element according to the invention,

FIG. 7 shows a second schematic cross-section of the charged particleblocking element according to the embodiment of FIG. 6 ,

FIG. 8 shows a schematic cross-section of a charged particle blockingelement provided with cooling channels according to an embodiment,

FIG. 9 shows a schematic top-view of an embodiment of a charged particleblocking element according to the invention,

FIG. 10A shows a schematic top-view of a further embodiment of a chargedparticle blocking element according to the invention,

FIG. 10B shows a schematic cross-section along the line VII-VII in FIG.10A,

FIG. 11 schematically illustrates a method of manufacturing asemiconductor device, and

FIG. 12 schematically illustrates a method of inspecting a target.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic overview of an example of an exposure apparatus100 for projecting one or more charged particle beams onto a target 110.Such an exposure apparatus may be part of a charged particle multi-beamlithography system, a charged particle multi-beam inspection system, ora charged particle multi-beam microscope. In particular it may be anelectron beam system, although the teaching applies to other types ofcharged particles as well.

The exposure apparatus 100 as shown in FIG. 1 comprises a chargedparticle optical arrangement comprising a charged particle source 101for generating a charged particle macro beam 111. The charged particlesource 101 in this particular example is arranged for generating adiverging charged particle macro beam which is directed to a collimatorlens 102 for focusing and/or collimating the charged particle macro beam111. In some embodiments the charged particle source 101 is an electronsource.

Downstream the collimator lens 102, the charged particle opticalarrangement comprises an aperture array element 104 which comprises anarray of apertures 1041 for splitting the charged particle macro beam111 into a plurality of charged particle beams 112. The aperture array104 comprises a charged particle blocking element according to theinvention, which in this embodiment is a current limiting element. Thecharged particle blocking element comprises a substrate 1042 comprisingthe array of apertures 1041 and is provided with an absorbing layer 1043comprising Boron, Carbon or Beryllium. The absorbing layer 1043 isarranged on a surface of the substrate 1042 which is facing the chargedparticle source 101. As schematically shown in FIG. 1 , the collimatedmacro beam 111 impinges on the aperture array element 104, in particularon the absorbing layer 1043 thereof, which blocks part of the collimatedmacro beam 111 while forming the plurality of charged particle beams 112by the part of the macro beam passing through the apertures 1041. In theexample of FIG. 1 , only three beams 112 have been depicted for clarityreasons, but the number of beams is generally in the range of hundreds,thousands or even ten-thousands.

The charged particle blocking element according to the invention hasbeen found to be particularly advantageous in use as a current limitingelement, in particular with the aperture array element 104 as describedabove. Alternatively or additionally, the charged particle blockingelement may be applied at other locations within the apparatus, as willbe described below.

Further towards the target 110, the charged particle optical arrangementcomprises a modulation aperture array 105 for generating a plurality ofcharged particle sub-beams 115 from each of the charged particle beams112. In between the aperture array 104 and the modulation aperture array105, a condenser lens array 103 (or set of condenser lens arrays) isprovided for focusing the charged particle beams 112 on a correspondingopening in a beam stop array 108 located downstream the modulationaperture array 105.

In this example, the aperture array 105 is illustrated as producingthree sub-beams 115, 116 from each charged particle beam 112. Inpractice the number of sub-beams 115 which are generated from eachcharged particle beam 112 are generally much larger than three. In apractical embodiment around fifty sub-beams (for example 49 sub-beamsgenerated by a 7×7 aperture array) are generated from each chargedparticle beam 112. In other embodiments two hundred or more sub-beamsmay be generated.

The modulation aperture array 105 may also comprise a charged particleblocking element or current limiting element according to the invention.This is, however, not shown in detail in FIG. 1 .

The modulation aperture array 105, which is part of the charged particleoptical arrangement, comprises an array of deflectors which areconfigured for individually deflecting the charged particle sub-beams116 such as to be blocked by the beam stop array 108 or for allowing thecharged particle sub-beams 115 to pass through the correspondingaperture of the beam stop array 108 undeflected.

The beam stop array 108 comprises an array of apertures 1081, which arearranged to allow the charged particle sub-beams 115 to pass when notdeflected by the modulation aperture array 105. The charged particlesunbeams 116 which are deflected by the modulation aperture array 105are directed on to the surface of the beam stop array 108 facing thecharged particle source 101, such as to be blocked by the beam stoparray 108. In this example, the beam stop array 108 comprises a chargedparticle blocking element according to the invention, which comprises asubstrate 1082 comprising apertures 1081 and being provided with anabsorbing layer 1083 of a material comprising Boron, Carbon orBeryllium. The absorbing layer 1083 is arranged on a surface of thesubstrate 1082 which is facing the charged particle source 101 and whichreceives the sub-beams 116 to be blocked. As schematically indicated inFIG. 1 , the absorbing layer 1083 is arranged spaced apart from, and innear vicinity of, the apertures 1081 of the beam stop array 108.

Subsequently, the charged particle optical arrangement comprises aprojection lens or projection lens array 109 for projecting the chargedparticle sub-beams 115, which have passed the beam stop array 108, ontothe surface of a target 110. The charged particle optical arrangementmay further comprise one or more scanning deflector arrays (not shown)for scanning the sub-beams 115 over the surface of the target 110 whileexposing said target 110.

In a charged particle multi-beam lithography system, a charged particlemulti-beam inspection system, or a charged particle multi-beammicroscope, the target 110 is usually arranged on top of a stage 120,which allows accurately positioning and moving the target 110 withrespect to the charged particle optical arrangement.

As clearly indicated in FIG. 1 , the substrates 1042, 1082 with anabsorbing layer 1043, 1083 are arranged for blocking at least a part ofthe charged particle beam 111, 116 from the charged particle source 101,wherein the at least a part of the charged particle beam 111, 116 thatis blocked falls at least partially onto the absorbing layer 1043, 1083of the charged particle blocking element. Accordingly, the total currentin the charged particle beam(s) above the charged particle blockingelements is higher than the total current in the charged particlebeam(s) below the charged particle blocking elements. The chargedparticle blocking elements, in particular the aperture array 104, themodulation aperture array 105, and the beam stop array 108, are currentlimiting elements of the exposure apparatus 1.

In some embodiments the collimator lens 102, at least the part thereofwhich is close to the aperture array 104, may comprise a chargedparticle blocking element according to the invention, which comprises asubstrate 1021 provided with an absorbing layer 1022 and comprising atleast one aperture for passage of the macro beam 111. In the illustratedembodiment, the absorbing layer 1022 is arranged on a surface of thesubstrate 1021 facing the aperture array 104, since this in use mayfunction as a charged particle source for backscattered chargedparticles from the part of the charged particle beam which does not passthrough apertures 1041 and/or for secondary electrons which may becreated in the charged particle optical arrangement by incidence of thecharged particle beam 111 on the aperture array element 104, e.g. bythese charged particles being backscattered and impinging on othercomponents within the system.

Also the condenser lens array 103, at least the part thereof which isclosest to the modulation aperture array 105, may comprise a chargedparticle blocking element according to the invention, which comprises asubstrate 113 comprising at least one aperture and an absorbing layer114 of Boron, Carbon or Beryllium. The absorbing layer 114 is arrangedon a surface of the substrate 113 which is facing the modulationaperture array 105, which in use may function as a source ofbackscattered and/or secondary electrons which may be created in thecharged particle optical arrangement upon incidence of the chargedparticle beams 112 on the modulation aperture array 105.

Further, the charged particle blocking element may be used as a shutter107, arranged between the charged particle source 101 and the collimatorlens 102, in a substantially horizontally moveable way, to function as asource shutter. In this case the charged particle blocking element istypically not provided with an aperture. By moving it into the chargedparticle beam path the charged particle beam from the charged particlesource 101 is blocked, enabling temporarily shutting off the chargedparticle beam without turning off the charged particle beam source, e.g.during position adjustment and/or replacement of elements downstream thecharged particle source.

The charged particle blocking element may also be used as a shutter 108,functioning as a beam shutter, located between the modulation aperturearray 105 and the beam stop array 108. Such shutter finds application inblocking one or more groups of beams 115, 116, for example in case of anon-optimally functioning modulation aperture array 105. This shuttermay be realized by a charged particle blocking element not provided withapertures, and may be entered into the charged particle beam paths toshut off one or more groups of charged particle beams 115, 116.Alternatively, the charged particle blocking element may be providedwith one or more apertures, enabling selectively blocking one or moregroups of charged particle beams 115, 116 while allowing passage ofother groups of charged particle beams 115, 116.

FIG. 2 schematically shows a charged particle inspection system ormicroscope, for example an electron microscope, comprising a chargedparticle blocking element according to the invention. Such microscopesand inspection systems have a wide range of applications, e.g. insemiconductor device manufacturing. The apparatus comprises a chargedparticle source 201 generating a charged particle beam 202 and chargedparticle optics 203 projecting the charged particle beam 202 onto atarget 210, also referred to as sample, which is to be inspected oranalyzed. The target 210 is typically arranged on a stage (not shown)which is movable with respect to the charged particle optics 203. Thecharged particle optics 203 comprises various charged particle opticalelements and components, including electrostatic and/or electromagneticlens elements, for influencing the charged particle beam, as known inthe art. In some systems the charged particle beam 202 is split into aplurality of individual beams (not shown), which are directed onto thetarget. One or more different detectors 204, 205 are provided fordetecting various signals 206, 207 resulting from the interaction of thecharged particle beam with the target 210. Such signals encompass, forexample, secondary electrons, Auger electrons, backscattered chargedparticles, X-rays, cathodoluminescence, etc.

The inspection system further comprises a shutter element 10, realizedby a charged particle blocking element according to the invention. Theshutter element 10 is arranged for temporarily shutting off the chargedparticle source. Alternatively or additionally, the charged particleblocking element of the invention can be provided within the chargedparticle optics 203, for example as a current limiting element.Alternatively or additionally, a shutter element 10 may be arranged fortemporarily closing off the charged particle optics and/or detector areafrom a target space.

Examples of known inspection systems and/or electron microscopes can befound in U.S. Pat. No. 7,732,762 B2, U.S. Pat. No. 6,844,550 B1, and A.L. Eberle et al., “High-resolution, high-throughput imaging with amultibeam scanning electron microscope”, Journal of Microscopy, Vol.259, Issue 2, 2015, pp. 114-120. In accordance with the above, in thesesystems the charged particle blocking element according to the inventionmight be used, for example as a shutter downstream the electron sourceor electron gun, and/or as aperture array, beam splitter or beamlimiting aperture.

Various embodiments of the charged particle blocking element accordingto the invention are illustrated in FIGS. 3-10 and described below. Thecharged particle blocking elements described with reference to FIGS. 1-2may be charged particle blocking elements according to any one or moreof these embodiments.

FIG. 3 shows a schematic cross section of a charged particle blockingelement 10 according to an embodiment. The charged particle blockingelement 10 comprises a substrate 11 having an electrically conductivesurface on which an absorbing layer 13 is provided. In the illustratedembodiment, the electrically conductive surface is provided by anelectrically conductive layer 14 applied on a surface of the substrate11. The absorbing layer 13 is subsequently applied on the conductivelayer 14. The absorbing layer 13 advantageously is a Boron layer or aBoron Nitride layer, although other materials for example comprisingCarbon (C) or Beryllium (Be) can also be used. The substrate 11 may be asilicon substrate, and the electrically conductive layer 14 a Molybdenumlayer.

As discussed above, the thickness of the absorbing layer is important.FIG. 4 schematically illustrates a path of an electron impinging on acharged particle blocking element comprising an electrically conductivesubstrate 11 provided with an absorbing layer 13. An analogous situationapplies to the element illustrated in FIG. 3 . The electron e⁻ impingeson the surface of the charged particle blocking element 10′. As theelectron e⁻ impinges on the absorbing layer 13, it may be absorbed bythis layer. As the electron is absorbed, it enters into the absorbinglayer. In order for the electron to more likely be absorbed into thelayer than backscattered by the underlying surface 12 the absorbinglayer has, to be sufficiently thick. In order to avoid chargeaccumulation in the absorbing layer 13 as a result of the absorption ofthe electron, the charge must be removed from the absorbing layer. Asdescribed above, a layer comprising for example Boron is typically apoor conductor. If the layer is sufficiently thin, the electron chargewill pass through the absorbing layer and reach the surface 12 of theelectrically conductive substrate 11, which in the example is connectedto electric ground. The possibility of charge transport through theabsorbing layer to the underlying electrically conductive surfacedecreases with increasing thickness of the absorbing layer. Theinventors have found that a thickness of the absorbing layer should beof a few hundred nanometers, for example around 200 nm.

FIG. 5 shows a schematic cross-section of a charged particle blockingelement 20. This charged particle blocking element can for example beused for blocking at least a part of a charged particle beam from acharged particle source. The charged particle blocking element 20 can beused as a current limiting element, the aperture 22 functioning as acurrent limiting aperture. The charged particle blocking element 20comprises a substantially flat substrate 21 comprising at least oneaperture 22. The substrate 21 is provided with an absorbing layer 23 ofa material comprising Boron, Carbon or Beryllium. Preferably, theabsorbing layer 23 is a coating of Boron, Boron Nitride or SiliconCarbide. The absorbing layer 23 is arranged to substantially cover anarea on said substrate 21 which area at least comprises a part of saidsubstrate which in use is arranged

facing the charged particle source 101, for example on the aperturearray 104 and/or on the beam stop array 108 of FIG. 1 , or

facing the aperture array 104 or the modulation aperture array 105, forexample as a part of the collimator lens 102 and/or as a part of thecondenser lens array 103, respectively.

The substrate 21 according to this embodiment comprises an electricallyconductive material, which enables the removing of electrical chargefrom the absorbing layer 23. In use, such a substrate 21 is suitablyconnected to a controlled electrical potential or to ground potential 26via a connecting part 25, to enable the removal of electrical charge inthe absorbing layer 23 via electrical conduction through said substrate21. It is noted that the electrically conductive material within themeaning of this embodiment may also comprise a highly dopedsemiconductor material. Accordingly, the substrate 21 may comprise ahighly doped Silicon wafer, for example.

FIG. 6 shows a schematic cross-section of a charged particle blockingelement 30 according to another embodiment. The charged particleblocking element 30 comprises a substantially flat substrate 31comprising at least one aperture 32. The substrate 31 is provided withan absorbing layer 33 of a material comprising Boron, Carbon orBeryllium. Preferably the absorbing layer 23 is a coating of Boron,Boron Nitride or Silicon Carbide. The absorbing layer 33 is arranged tosubstantially cover an area on said substrate 31 which area at leastcomprises a part of said substrate, and may in use be arranged in asimilar manner as described for the charged particle blocking element ofFIG. 5 .

The charged particle blocking element 30 according to this embodiment isprovided with an electrically conductive layer 34. The electricallyconductive layer 34 is arranged in between the substrate 31 and theabsorbing layer 33. In use, the electrically conductive layer 34 isconnected to ground potential 36, or to a controlled electricalpotential, via a connecting part 35, as schematically shown in thecharged particle blocking element 30 with multiple apertures 32 of FIG.7 . Connecting the electrically conductive layer 34 to ground potential36 enables the removal of electrical charge from the absorbing layer 33via electrical conduction through the electrically conductive layer 34.The electrically conductive layer 34 comprises, for example, Molybdenumor Chromium. Although only one aperture 32 is illustrated in FIG. 6 ,the charged particle blocking element may comprise a plurality ofapertures 32 as illustrated in FIG. 7 .

In particular for a charged particle blocking element 30 with multipleapertures 32, as schematically shown in FIG. 7 , it is desirable thatthe substrate 31 comprises a Si wafer, which is readily available andprovides a highly flat and mechanically robust substrate with awell-defined thickness.

FIG. 8 shows a further embodiment of a charged particle blocking element40. The charged particle blocking element 40 comprises a substantiallyflat substrate 41 comprising at least one aperture 42, preferably aplurality of apertures 42. The substrate 41 is provided with anabsorbing layer 43 of a material comprising Boron, Carbon or Beryllium,preferably a coating of Boron, Boron Nitride or Silicon Carbide. Theabsorbing layer 43 is arranged to substantially cover an area on saidsubstrate 41 which area at least comprises a part of said substrate, andis in use typically arranged in a similar manner as described for thecharged particle blocking elements of FIG. 5 .

The charged particle blocking element 40 according to this embodiment isprovided with one or more cooling conduits 45 for cooling the substrate41. The cooling conduits 45 are arranged in thermal contact with thesubstrate 41 and/or with a further electrically and/or thermallyconductive layer 46.

The further conductive layer 46 is arranged in contact with theabsorbing layer 43 and with the cooling conduits 45 and may comprise amaterial having a high thermal conductivity to provide a heat conductingpath from the absorbing layer 43 to the cooling conduits 45.

In addition or alternatively, the further conductive layer 46 maycomprise a material with a high electrical conductivity to provide anelectrically conducting path from the absorbing layer 43 and/or from theelectrically conductive layer 44 which is arranged between the substrate41 and the absorbing layer 43, to the cooling conduits 45, which in useare connected to ground potential 47.

As schematically shown in FIG. 8 , the cooling conduits 45 are arrangedat a side of the substrate 41 facing away from the absorbing layer 43.However, the cooling conduits 45 can also be arranged at the same sideof the substrate 41 as the absorbing layer 43, preferably at a positionspaced apart from the apertures 42. In such an arrangement the absorbinglayer 43 can be arranged in direct contact with the cooling conduits 45and a further conductive layer 46 as in the example of FIG. 8 is notnecessary.

FIG. 9 shows a schematic top-view of an embodiment of a charged particleblocking element 50 according to the invention. The charged particleblocking element 50 comprises a substantially flat substrate 51comprising an array 56 of apertures arranged in an array area 52. Thesubstrate 51 is a Silicon wafer which is provided with a coating 53 ofMolybdenum as an electrically conductive layer. On top of the Molybdenumcoating 53, a coating of Boron 54 is arranged as an absorbing layer. Asschematically shown in FIG. 9 , the absorbing layer, in particular theboron coating 54, is arranged spaced apart from the apertures of theaperture array 56. In particular, the boron coating 54 is arrangedspaced apart from the array area 52. The absorbing layer 54 may bearranged as one single area, or it may be provided by a plurality ofareas separated by parts 55 of the electrically conductive coating 53not covered by an absorbing layer or coating.

In an embodiment of the invention, the charged particle blocking element50 is used as an aperture array element 104 forming a plurality ofcharged particle beams from a macro-beam, in particular as the aperturearray element 104 of a charged particle exposure system 100. An exampleof a cross section of the macro-beam 111 on the charged particleblocking element 50 when used as an aperture array element 104 isindicated by the circle 57. As can be seen, a large part of the beamfalls on an area covered by the absorbing layer 54. That is, a largepart of the blocked part of the charged particle beam impinges on theabsorbing layer 54, to be absorbed by this.

FIG. 10A shows a schematic top-view of a further embodiment of a chargedparticle blocking element 60 according to the invention. FIG. 10B showsa schematic cross section along the line VII-VII in FIG. 10A.

The charged particle blocking element 60 comprises a substantially flatsubstrate 61 comprising a plurality of arrays of apertures arranged indifferent array areas 62. The substrate 61 is a Silicon wafer which isprovided with a coating 63 of Molybdenum as an electrically conductivelayer. On top of the Molybdenum coating 63, a coating of Boron 64 isarranged as an absorbing layer. As schematically shown in FIGS. 10A and10B, the absorbing layer 64, is arranged spaced apart from the aperturesof the aperture array. In particular, the boron coating 64 is arrangedspace apart from the array areas 62. As schematically indicated in FIGS.10A and 10B, the boron coating 64 also at least partially extends inareas 65 in between the array areas 62.

The absorbing layer 64 may be arranged as one single area, or it may beprovided by a plurality of areas separated by parts 66 of theelectrically conductive coating 63 not covered by an absorbing layer orcoating.

This charged particle blocking element 60 may for example be used as anaperture array splitting a charged particle macro beam into a pluralityof charge particle beams. In an embodiment of the present invention, itis employed in the aperture array element 104 of a charged particleexposure system as illustrated in FIG. 1 . An example of a cross sectionof the macro-beam 111 on the charged particle blocking element 60 whenused as an aperture array 104 is indicated by the circle 67. As can beseen, a large part of the blocked beam is blocked by the absorbing layer64.

FIG. 11 schematically illustrates the steps of a method 80 ofmanufacturing a semiconductor device by means of an exposure apparatusas described above. In a first step 81, the wafer is placed downstreamof said charged particle optical arrangement. In a second step 82 thewafer is processed, including projecting an image or a pattern on saidwafer by means of a charged particle beam generated, shaped and/ormodulated by said charged particle optical arrangement. In a third step83 subsequent steps are performed in order to generate a semiconductordevice from the processed wafer. Such subsequent steps are known in theart.

FIG. 12 schematically illustrates the steps of a method 90 forinspecting a target by means of an exposure apparatus or inspectionsystem as described above. In a first step 91 the target is positioneddownstream the charged particle optical arrangement, and in a secondstep 92 a charged particle beam generated and shaped by said chargedparticle optical arrangement is directed towards the target. In a thirdstep 93 charged particles transmitted, emitted and/or reflected by saidtarget upon incidence of the charged particle beam on the target aredetected. In the fourth step 94 subsequent steps are performed in orderto inspect said target by means of data gathered during the step ofdetecting charged particles.

It is to be understood that the above description is included toillustrate the operation of the preferred embodiments and is not meantto limit the scope of the invention. From the above discussion, manyvariations will be apparent to one skilled in the art that would yet beencompassed by the scope of the present invention.

CLAUSES

C1. A charged particle blocking element for blocking charged particles,wherein the charged particle blocking element comprises a substrate,wherein at least a portion of a surface of the substrate is providedwith an absorbing layer comprising Boron (B), Carbon (C) or Beryllium(Be), wherein said absorbing layer is provided on an electricallyconductive surface.

C2. The charged particle blocking element according to clause C1,wherein said absorbing layer has a thickness sufficient to preventbackscattering of said charged particles from a portion of saidsubstrate located below said absorbing layer and thin enough forelectrical charge of said charged particles to be received by saidelectrically conductive surface.

C3. The charged particle blocking element according to clause C1 or C2,wherein said absorbing layer has a thickness between 100 nm to 500 nm.

C4. The charged particle blocking element according to clause C3,wherein said absorbing layer has a thickness between 150 and 250 nm.

C5. The charged particle blocking element according to any one of thepreceding clauses, wherein the absorbing layer is a Boron layer, a BoronNitride layer or a Silicon Carbide layer.

C6. The charged particle blocking element according to any one of thepreceding clauses, wherein at least a part of the substrate iselectrically conductive.

C7. The charged particle blocking element according to clause C6,wherein the substrate comprises a connecting part for connecting the atleast a part of the substrate which is electrically conductive to avoltage supply or to ground potential.

C8. The charged particle blocking element according to any one of thepreceding clauses, wherein the substrate is provided with anelectrically conductive layer, wherein the electrically conductive layeris at least partially arranged in between the substrate and theabsorbing layer.

C9. The charged particle blocking element according to clause C8,wherein the electrically conductive layer comprises Molybdenum (Mo) orChromium (Cr).

C10. The charged particle blocking element according to clause C8 or C9,comprising an electrically conductive connecting part which is connectedto the electrically conductive layer.

C11. The charged particle blocking element according to any one of thepreceding clauses, wherein the substrate comprises a Silicon (Si) wafer.

C12. The charged particle blocking element according to any one of thepreceding clauses, wherein said substrate is provided with at least oneaperture allowing passage of charged particles.

C13. The charged particle blocking element according to clause C12,wherein the substrate is provided with a plurality of said apertures,wherein said apertures are arranged to form one or more aperture arrays,each of said one or more aperture arrays being arranged in acorresponding array area of said substrate.

C14. The charged particle blocking element according to clause C13,wherein said absorbing layer at least partly encloses said array areas.

C15. The charged particle blocking element according to clause C13 orC14, wherein each array area is at least partly enclosed by saidabsorbing layer.

C16. The charged particle blocking element according to any one ofclauses C13 to C15, wherein said absorbing layer is further arranged atleast partly within each array area.

C17. The charged particle blocking element according to any one of theclauses C12 to C16, wherein the absorbing layer is arranged spaced apartfrom the at least one aperture.

C18. The charged particle blocking element according to any one of thepreceding clauses, wherein the charged particle blocking elementcomprises cooling conduits for cooling at least the substrate,preferably wherein the cooling conduits are arranged in thermal contactwith the absorbing layer and/or the substrate.

C19. The charged particle blocking element according to clause C18,wherein the substrate is provided with a further electrically and/orheat conductive layer, wherein the further electrically and/or heatconductive layer is arranged in contact with the absorbing layer andwith the cooling conduits.

C20. Current limiting element for use in a charged particle exposureapparatus, said current limiting element comprising a substratesubstantially not allowing transmission of charged particles, saidsubstrate being provided with one or more apertures extending throughsaid substrate from a first surface to a second surface of saidsubstrate, said one or more apertures allowing passage of chargedparticles,

wherein at least a portion of said first surface is provided with anabsorbing layer comprising Boron (B), Carbon (C) or Beryllium (Be),

wherein said absorbing layer is provided on an electrically conductivesurface.

C21. Current limiting element according to clause C20, wherein saidabsorbing layer at least partially encloses an area of said firstsurface in which said one or more apertures are arranged.

C22. The current limiting element according to clause C20 or C21,wherein the absorbing layer is arranged spaced apart from the one ormore aperture.

C23. The current limiting element according to any one of clauses C20 toC22, wherein said absorbing layer has a thickness sufficient to preventbackscattering of said charged particles from a portion of saidsubstrate located below said absorbing layer and thin enough forelectrical charge of said charged particles to be received by saidelectrically conductive surface.

C24. The current limiting element according to any one of clauses C20 toC23, wherein said absorbing layer has a thickness of 100 nm to 500 nm.

C25. The current limiting element according to clause C24, wherein saidabsorbing layer has a thickness of 150 nm to 250 nm.

C26. The current limiting element according to any one of the precedingclauses, wherein the absorbing layer is a Boron layer, a Boron Nitridelayer or a Silicon Carbide layer.

C27. The current limiting element according to any one of the clausesC20-C26, wherein at least a part of the substrate is electricallyconductive.

C28. The current limiting element according to any one of clauses C20 toC27, wherein the substrate is provided with an electrically conductivelayer, wherein the electrically conductive layer is at least partiallyarranged in between the substrate and the absorbing layer.

C29. The current limiting element according to clause C28, wherein theelectrically conductive layer comprises Molybdenum (Mo) or Chromium(Cr).

C30. The current limiting element according to any one of clauses C27 toC29, comprising an electrically conductive connecting part forconnecting the electrically conductive substrate or the electricallyconductive layer to a voltage supply or to ground potential.

C31. The current limiting element according to any one of clauses C20 toC30, wherein the substrate comprises a Silicon (Si) wafer.

C32. The current limiting element according to any one of clauses C20 toC31, further comprising cooling conduits for cooling at least thesubstrate, preferably wherein the cooling conduits are arranged inthermal contact with the absorbing layer and/or the substrate.

C33. The current limiting element according to clause C32, wherein thesubstrate is provided with a further electrically conductive and/or heatconductive layer, wherein the further electrically conductive and/orheat conductive layer arranged in contact with the absorbing layer andwith the cooling conduits.

C34. A shutter element for blocking a charged particle beam, saidshutter element comprising a substrate, at least a portion of which isprovided with an absorbing layer comprising Boron (B), Carbon (C) orBeryllium (Be), wherein said absorbing layer is provided on anelectrically conductive surface on said substrate.

C35. The shutter element according to clause C34, wherein said absorbinglayer has a thickness sufficient to prevent backscattering of saidcharged particles from said electrically conductive surface locatedbelow said absorbing layer and thin enough for electrical charge of saidcharged particles to be received by said electrically conductivesurface.

C36. The shutter element according to clause C34 or C35, wherein saidabsorbing layer has a thickness between 100 nm to 500 nm.

C37. The shutter element according to clause C36, wherein said absorbinglayer has a thickness between 150 and 250 nm.

C38. The shutter element according to any one of clauses C34 to C37,wherein the absorbing layer is a Boron layer, a Boron Nitride layer or aSilicon Carbide layer.

C39. The shutter element according to any one of clauses C34 to C38,wherein at least a part of the substrate is electrically conductive.

C40. The shutter element according to any one of clauses C34 to C39,wherein the substrate is provided with an electrically conductive layer,wherein the electrically conductive layer is at least partially arrangedin between the substrate and the absorbing layer.

C41. The charged particle blocking element according to clause C40,wherein the electrically conductive layer comprises Molybdenum (Mo) orChromium (Cr).

C42. The charged particle blocking element according to any one ofclauses C39 to C41, comprising an electrically conductive connectingpart which is connected to the part of the substrate which iselectrically conductive or to the electrically conductive layer.

C43. An exposure apparatus for projecting a charged particle beam onto atarget, said exposure apparatus comprising a charged particle opticalarrangement for forming a charged particle beam and projecting at leasta part of the charged particle beam onto the target, the chargedparticle optical arrangement comprising:

-   -   a charged particle source for generating the charged particle        beam, and    -   a charged particle blocking element according to any one of the        claims 1 to 19, which charged particle blocking element enables        blocking at least a part of the charged particle beam from the        charged particle source, a current limiting element according to        any one of claims 20 to 33 arranged to limit a charged particle        current of said charged particle beam, and/or a shutter element        according to any one of claims 34 to 42 for temporarily shutting        off at least a part of said charged particle beam.

C44. The exposure apparatus according to clause C43, wherein theabsorbing layer of the charged particle blocking element, the currentlimiting element, and/or the shutter element is arranged at a surface ofthe substrate facing the charged particle source or facing towards asource of backscattered charged particles and/or secondary electrons.

C45. The exposure apparatus according to clause C44, wherein the shutterelement is arranged as a shutter for said charged particle source.

C46. The exposure apparatus according to any one of clauses C43 to C45comprising the current limiting element according to any one of clausesC20 to C33, wherein the current limiting element comprises an array ofapertures arranged for splitting the charged particle beam into multiplecharged particle beams.

C47. The exposure apparatus according to any one of the clauses C43 toC46, further comprising a modulation deflector for deflecting thecharged particle beam onto the charged particle blocking element,wherein the modulation deflector and the charged particle blockingelement are arranged to allow the charged particle beam to pass theaperture of the charged particle blocking element when the chargedparticle beam is not deflected by the deflector, and to at leastpartially block the charged particle beam by the charged particleblocking element when the charged particle beam is deflected by thedeflector, or vice versa.

C48. A charged particle lithography system comprising an exposureapparatus according to any one of the clauses C43 to C47.

C49. A charged particle inspection system or charged particle microscopecomprising an exposure apparatus according any to one of the clauses C43to C48.

C50. A method for projecting a charged particle beam onto a target usingan exposure apparatus according to any one of the clauses C43 to C49,wherein the method comprises the step of blocking at least a part of thecharged particle beam from the charged particle source, wherein at leasta part of the charged particle beam that is blocked falls onto theabsorbing layer of the charged particle blocking element or the currentlimiting element.

C51. Method of manufacturing a semiconductor device by means of anexposure apparatus according to any one of the clauses C43 to C49, themethod comprising the steps of:

-   -   placing a wafer downstream of said charged particle optical        arrangement;    -   processing said wafer including projecting an image or a pattern        on said wafer by means of a charged particle beam generated,        shaped and/or modulated by said charged particle optical        arrangement; and    -   performing subsequent steps in order to generate a semiconductor        device by means of said processed wafer.

C52. Method for inspecting a target by means of an exposure apparatusaccording to any one of the clauses C43 to C49, the method comprisingthe steps of:

-   -   positioning said target downstream said charged particle optical        arrangement;    -   directing a charged particle beam generated and shaped by said        charged particle optical arrangement towards said target;    -   detecting charged particles transmitted, emitted and/or        reflected by said target upon incidence of the charged particle        beam on the target; and    -   performing subsequent steps in order to inspect said target by        means of data gathered during the step of detecting charged        particles.

The invention claimed is:
 1. An exposure apparatus for projecting acharged particle beam onto a target, the exposure apparatus comprising acharged particle optical arrangement for forming a charged particle beamand projecting at least a part of the charged particle beam onto thetarget, the charged particle optical arrangement comprising: a chargedparticle source for generating the charged particle beam, and aplurality of charged particle blocking elements configured to block atleast a part of the charged particle beam from the charged particlesource, wherein the charged particle blocking elements comprise asubstrate, at least one of the substrates comprising at least oneaperture allowing passage of at least a part of the charged particlebeam, and at least one of the charged blocking elements comprising aplurality of apertures configured to form a plurality of beams from thecharged particle beam, wherein a portion of a surface of at least one ofthe substrates comprises an absorbing layer of a material comprisingCarbon, and/or Beryllium (Be) configured to absorb at least part ofcharged particles impinging the surface, wherein the absorbing layer iselectrically conductive and configured to remove absorbed electricalcharges.
 2. The exposure apparatus according to claim 1, wherein theabsorbing layer is arranged spaced apart from the at least one aperture.3. The exposure apparatus according to claim 1, wherein the absorbinglayer has a thickness sufficient to prevent backscattering of thecharged particles from a portion of the substrate located below theabsorbing layer.
 4. The exposure apparatus according to claim 1, whereinthe absorbing layer is a Silicon Carbide.
 5. The exposure apparatusaccording to claim 1, wherein at least a part of the substrate iselectrically conductive.
 6. The exposure apparatus according to claim 5,wherein the substrate comprises a connecting part for connecting the atleast a part of the substrate which is electrically conductive to avoltage supply or to ground potential.
 7. The exposure apparatusaccording to claim 5, wherein the substrate is provided with anelectrically conductive layer, wherein the electrically conductive layeris at least partially arranged in between the substrate and theabsorbing layer.
 8. The exposure apparatus according to claim 7, whereinthe electrically conductive layer comprises Molybdenum (Mo) or Chromium(Cr).
 9. The exposure apparatus according to claim 7, further comprisingan electrically conductive connecting part that is connected to theelectrically conductive layer.
 10. The exposure apparatus according toclaim 1, wherein the plurality of apertures are arranged to form one ormore aperture arrays, each aperture array arranged in a correspondingarray area of the substrate.
 11. The exposure apparatus according toclaim 10, wherein the absorbing layer at least partly encloses the oreach array area; the or each array area is at least partly enclosed bythe absorbing layer; and/or the absorbing layer is further arranged atleast partly within the or each array area.
 12. The exposure apparatusaccording to claim 1, wherein the plurality of the charged particleblocking elements are comprised in a condenser lens array configured tofocus the charged particle beams.
 13. The exposure apparatus accordingto claim 1, wherein the plurality of the charged particle blockingelements are comprised in a collimator lens configured to focus thecharged particle beam, to collimate the charged particle beam, or bothto focus and to collimate the charged particle beam.
 14. The exposureapparatus according to claim 1, wherein the charged particle blockingelement comprises cooling conduits for cooling at least the substrate.15. The exposure apparatus according to claim 1, wherein the chargedparticle blocking element is a current limiting element arranged tolimit a charged particle current of the charged particle beam.
 16. Theexposure apparatus according to claim 15, wherein the absorbing layer atleast partially encloses an area of a surface of the substrate in whichthe one or more apertures are arranged and preferably wherein the one ormore apertures has a diameter smaller than a diameter of the chargedparticle beam at the current limiting element.
 17. The exposureapparatus according to claim 16, wherein the absorbing layer of thecharged particle blocking element is arranged at the surface of thesubstrate facing the charged particle source or facing towards a sourceof backscattered charged particles and/or secondary electrons.
 18. Theexposure apparatus according to claim 1, further comprising a modulationdeflector for deflecting the charged particle beam onto the chargedparticle blocking element, wherein the modulation deflector and thecharged particle blocking element are arranged to allow the chargedparticle beam to pass the aperture of the charged particle blockingelement when the charged particle beans is not deflected by thedeflector, and to at least partially block the charged particle beam bythe charged particle blocking element when the charged particle beam isdeflected by the deflector, or vice versa.
 19. An exposure apparatus forprojecting a charged particle beam onto a target, the exposure apparatuscomprising a charged particle optical arrangement for forming a chargedparticle beam and projecting at least a part of the charged particlebeam onto the target, the charged particle optical arrangementcomprising: a charged particle source for generating the chargedparticle beam, and a plurality of charged particle blocking elementsconfigured to block at least a part of the charged particle beam fromthe charged particle source; the charged particle blocking elementscomprising a substrate, at least one of the substrates comprising aplurality of apertures configured to allow passage of at least a part ofthe charged particle beam in a plurality of beams, at least one of thecharged blocking elements being a beam splitter configured to form theplurality of beams from the charged particle beam, wherein the substrateof the beam splitter has at least a portion with an absorbing layercomprising Carbon (C), Boron (B), and/or Beryllium (Be), the absorbinglayer provided on an electrically conductive surface on the substrate ofthe beam splitter, and the electrically conductive surface configured toremove absorbed electrical charges from the absorbing layer.
 20. Acharged particle inspection system or charged particle microscope forprojecting a charged particle beam onto a target, the charged particleinspection system or charged particle microscope comprising an exposureapparatus comprising a charged particle optical arrangement for forminga charged particle beam and projecting at least a part of the chargedparticle beam onto a target; and a stage configured for arrangement ofthe target thereon, the charged particle optical arrangement comprising:a charged particle source for generating the charged particle beam, anda plurality of charged particle blocking elements configured to block atleast a part of the charged particle beam from the charged particlesource, the charged particle blocking elements comprising a substrate,the substrates comprising at least one aperture allowing passage of atleast a part of the charged particle beam, wherein at least one of thecharged blocking elements comprises an absorbing layer of a materialcomprising Carbon, Boron (B), and/or Beryllium (Be) on the correspondingsubstrate at least part of the portion of the surface of thecorresponding substrate comprises an electrically conductive materialconfigured to remove absorbed electrical charges from the absorbinglayer.